The chemistry of triterpenes and related compounds. Part XLVII. Clarification of the nature of the tetracyclic triterpene acids of elemi resin

The literature concerning the tetracyclic triterpene acids of elemi resin is confused. The acids have been reexamined by modern techniques and shown to be 3-oxotirucalla-8,24-dien-21-oic acid (IV), the corresponding 3α- and 3β-hydroxy-acids (I and VI), and 3α-hydroxytirucalla-7,24-dien-21-oic acid (X). The 3α-hydroxy-Δ7- and -Δ8- acids are difficult to separate and occur in different samples of resin in varying proportions. It is suggested that the confusion has arisen because samples of α-elemolic acid used by different workers have been mixtures of varying proportions of the 3α-hydroxy-Δ7- and -Δ8-acids.The possible biogenesis of 3α-hydroxy-triterpenes is discussed.